1. Field of the Invention
The present invention relates to a machine for manufacturing or treating a material web, e.g., a paper or cardboard web, by guiding the web, either alone or with a transport belt over at least one heatable cylinder, the cylinder comprising a combustion unit being adapted to be heated with at least one of combustion gases and infrared radiation, and a process for drying a material web, in particular a paper or cardboard web, by guiding the web, either alone or with a transport belt over the at least one heatable cylinder and heating the heatable cylinder with a combustion unit comprising at least one of combustion gases and infrared radiation of a combustion unit
2. Discussion of Background Information
A directly heated cylinder utilized in a dryer section of a paper or cardboard machine to dry a paper or cardboard web guided over its surface is known from U.S. Pat. No. 5,553,391. A combustion unit that produces infrared radiation by burning gas heats the cylinder to temperatures usually ranging between 160.degree. C. and 450.degree. C., and is placed in the interior of the cylinder. The high energy input to dry the material web and the high costs for performing the drying process are disadvantages of this known system.
It is also known to heat the cylinder to temperatures of 130.degree. C. to approximately 200.degree. C. with steam. The energy input for drying the material web in this manner is lower than with direct heating of the cylinder. However, the temperatures that can be obtained via steam are limited to approximately 200.degree. C. Further, the associated costs for this type of system are significant because of extensive space requirements for the steam heating units required for heating of the cylinder, e.g., a piping system feeding the steam and the condensate, a heat exchanger, etc.
A dryer section is also known from EP 0 427 218 B 1 that consists of a steam-heated cylinder and blower boxes. Via the blower boxes, a hot gas, e.g., air, at an elevated temperature of between approximately 150.degree. C. and 450.degree. C. and at a high velocity of between approximately 50 m/s and 100 m/s is blasted onto the material web. In this manner, high evaporation rates are obtained on small surface areas. However, the energy input necessary to heat blown gas is usually so high that the total energy efficiency of this process, i.e., the combination of the dryer cylinder and blower boxes, is lower by several percentage points, than the drying process utilizing only steam heated cylinders.